Section
5
MAINTENANCE
5-1. INTRODUCTION
This section contains per iodic maintenance and perform ance test pr ocedures for the Multicarrier
Cellular Amplifier System. It also contains a list of test equipment required to perform the
identified tasks.
NOTE
Check your sales order and equipment warranty
before attempting to service or repair the unit. Do
not break the seals on equipm ent under warranty or
the warranty will be null and void. Do not return
equipment for warranty or repair service until proper
shipping instructions are received from the factory.
5-2. PERIODIC MAINTENANCE
Periodic maintenance requirem ents are listed in Table 5-1. Table 5-1 also lists the inter vals at
which the tasks should be performed.
WARNING
Wear proper eye protection to avoid
eye injury when using compressed air.
Table 5-1. Periodic Maintenance
TASK INTERVAL ACTION
Cleaning
Air Vents 30 Days Inspect and clean per para. 5-4.
Inspection
Cables and
Connectors
Performance Tests
5-3. TEST EQUIPMENT REQUIRED FOR TEST
Test equipment required to test the amplifier system is listed in Table 5-2. Equivalent test
equipment may be substituted for any item; k eep in mind that a thermistor type power meter is
required.
All RF test equipment must be calibrated to 0.05 dB
resolution. Any deviation from the nominal attenuation m ust
be accounted for and factored into all output readings.
12 Months Inspect signal and power cables
for frayed insulation. Check RF
connectors to be sure that they are
tight.
12 Months Perform annual test per para. 5-5.
NOTE
044-05055 Rev. A 5-1
Table 5-2. Test Equipment Required
NOMENCLATURE MANUFACTURER MODEL
Signal Generator RDL IMD-801D-03A
30 dB Attenuator, 500 Watt Weinschel Corp. 53-30-34
10 dB Attenuator, 20 Watt
Tenuline
(2 each)
Spectrum Analyzer H.P. 8560E
Coax Directional Coupler H.P. 778D
Power Meter/Sensor H.P. 437B/8481A
Network Analyzer H.P. 8753C
Current Probe
5-4. CLEANING AIR INLETS/OUTLETS
The air inlets and outlets should be cleaned every 30 days. If the equipment is operated in a
severe dust environment, they should be cleaned more often as necessary. Turn off DC power
source before rem oving fans. If dust and dirt are allowed to accumulate, the cooling eff iciency
may be diminished. Using either compressed air or a brus h with soft bristles , loosen and rem ove
accumulated dust and dirt from the air inlet panels.
5-5. PERFORMANCE TEST
Performance testing should be conducted every 12 months to ensure that the amplifier system
meets the operational specif ications listed in table 5-3. Also verify system perf ormanc e after any
amplifier m odule is replaced in the field. The test equipment required to perform the testing is
listed in table 5-2, and the test setup is shown in figure 5-1.
NOTE
The frequencies used in this test are typical for an am plifier with
a 25 MHz band from 869 MHz to 894 MHz. Select evenly spaced
F1, F2, F3, and F4 frequencies that cover the instantaneous
bandwidth of your system.
5-5.1. AMPLIFIER SYSTEM PERFORMANCE TEST.
This test is applicable to the MCR20XX Series (NTL107AC) subrack with two plug-in G3X-800
Series (NTL107AA) amplifier modules. To perform the test, proceed as follows:
1. Connect test equipment to the subrack as shown in figure 5-1.
NOTE
Do not apply any RF signals at this time.
2. Turn on signal generator and set frequency F1 to 880 MHz, F2 to 883 MHz, F3 to 886
MHz, and F4 to 889 MHz. Adjust each signal generator output so that the sum power
output from all four signal generators equals -4 dBm at the output of the 4-way combiner.
044-05055 Rev. A 5-2
Figure 5-1. Amplifier System Test Setup Diagram
SINGLE AMPLIFIER IMD TEST:
3. Adjust attenuator for an input signal at -l0 dBm. Turn on both amplifiers, and set RF ON
switch of amplifier number two to OFF. Reset first amplifier with the front panel RF ON
switch, and set switch to ON. Adjust variable attenuator to set amplifier power output on
power meter to 100 watts. Measure IMD on spectrum analyzer. IMD should be -65 dBc
min. Record test data in table 5-3. Set RF ON switch to OFF.
4. Repeat step 3 for amplifier number two.
TWO AMPLIFIER IMD AND CURRENT TEST:
5. Reset and turn on both amplifier modules. Adjust the variable attenuator to set power
output on power meter to 200 watts. Measure IMD on spectrum analyzer. IMD should be
-65 dBc min. Record test data in table 5-3.
6. With the amplifier modules set at 200 watts power output, use the current probe
(magnetic field type) and measure the dc current flow from the +27 Vdc power source.
Current should be 110 amps maximum. Record test data in table 5-3.
044-05055 Rev. A 5-3
GAIN TEST:
7. Disconnect spectrum analyzer from test setup, and connect the network analyzer.
8. Set network analyzer as follows:
• Power output to 5 dBm.
• Frequency start to 869 MHz.
• Frequency stop to 894 MHz.
• Normalize the network analyzer for gain and return loss.
9. Reset and turn on the channel 1 amplifier ; turn off channel 2 amplif ier. Check the gain
across the band from 869 MHz to 894 MHz. Gain should be between 30 and 50 dB.
Record test data in table 5-3.
10. Tu rn off the channel 1 am plifier and reset and tur n on the channel 2 amplif ier. Check the
gain across the band from 869 MHz to 894 MHz. Gain should be between 30 and 50 dB.
Record test data in table 5-3.
11. Rese t and turn on both amplifier modules and check the gain. T he gain of both amplifiers
should be 3 dB higher than in steps 9 and 10. Record test data in table 5-3.
HARMONICS TEST
12. With the power set at 200 watts power output, use the spectrum analyzer and check the
frequency band from 869 MHz to 894 MHz for harmonics. Harmonics should be -45 dBc
maximum. Record test data in table 5-3.
SPURIOUS TEST
13. With the power amplifier set at 200 watts power output, use the spectrum analyzer and
check the frequency band from 869 MHz to 894 MHz for spurious signals. Spurious
signals should be -60 dBc maximum. Record test data in table 5-3.
INPUT RETURN LOSS TEST:
14. Reset and turn on both amplifier m odules in the subr ack. Read and r ecord the S
loss measurem ent on network analyzer. Input return loss should be –14 dB minimum.
Record test data in table 5-3.
11
return
044-05055 Rev. A 5-4
Table 5-3. Multicarrier Cellular Amplifier System Test Data Sheet
DATE _________________________________
MCR20XX SERIES (NTL107AC) SUBRACK S/N ______________________________________
MODULE #1 S/N ________________________ MODULE #2 S/N ________________________
TEST CONDITIONS:
Load and Source Impedance: 50 Ohms
VSWR: < 1.2:1
Supply Voltage: +27 Vdc ±1.0 Vdc
TEST SPECIFICATION MIN MAX DATA
4-TONE IMD
One Module
4-TONE IMD
Two Modules
RF Gain
One Module
RF Gain
Two Modules
Gain Flatness
Harmonics
Spurious
Input Return
Loss
DC Power
Vcc = 27 Vdc
PO = 100 W
Freq.: 880, 883, 886, and 889
MHz
Vcc = 27 Vdc
PO = 200 W
Freq.: 880, 883, 886, and 889
MHz
Vcc = 27 Vdc
PO = 100 W
Freq. = 880 MHz
Vcc = 27 Vdc
PO = 200 W
Freq. = 880 MHz
Vcc = 27 Vdc ±1 Vdc
PO =200 W
869-894 MHz Band
Vcc = 27 Vdc
PO = 200 W
869-894 MHz Band
Vcc = 27 Vdc
PO =200 W
869-894 MHz Band
Vcc = 27 Vdc
PO = 200 W
869-894 MHz Band
Vcc = 27 Vdc
PO = 200 W
4 Tones
-65 dBc
-65 dBc
30 dB 50 dB
30 dB 50 dB
-0.6 dB +0.6 dB
-13 dBm
-60 dBc
-16 dB
110
Amps
12
1,2
12
1,2
1,2
1,2
1,2
1,2
1,2
PASS _________________________________ FAIL _______________________________
Tested by ______________________________
044-05055 Rev. A 5-5
5-6. FIELD REPLACEABLE PARTS AND MODULES
The following parts and modules can be replaced in the f ield on site by a qualified technician with
experience maintaining RF power amplifiers and similar equipment:
1. G3X-800 Series (NTL107AA) power amplifier modules
2. Cooling fans
5-6.1. G3X-800 SERIES (NTL107AA) MODULE
To replace a power amplifier module, proceed as follows:
1. Set both the RF ON On/Off/Reset switch and the power ON/OFF switch on the front panel
of the amplifier module to OFF.
2. Loosen two screws that secure amplifier module to subrack.
3. Use handle on front of module, and with a steady even pressure, pull module out of
subrack.
CAUTION
When removing the amplifier from the subrack, it is very
important to support the amplifier such that the rear of the
module does not suddenly drop when it disengages from the
track. A drop such as this could damage the module.
5-6.2. COOLING FANS
To replace a cooling fan, proceed as follows:
1. Remove amplifier module from subrack; see paragraph 5-6.1 preceding.
2. Loosen four snap fasteners that secure fan to amplif ier module. Disconnect fan power
connector from amplifier module.
3. Install replacement in reverse order of steps 1 and 2 above.
044-05055 Rev. A 5-6
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